1. Field of the Invention
This disclosure relates generally to apparatus and methods of broadcast teardown. More particularly, the disclosure relates to broadcast teardown of a direct link between stations (STAs) that were previously set up using the tunneled direct link setup (TDLS) protocol.
2. Description of the Related Art
The wireless communication environment in a home or an office typically comprises a number of independently developed radio access technologies and standards. These technologies were initially designed for target applications and they perform relatively well for these applications. In a typical home or office environment, an access to content, (e.g., web, video, etc.), is provided to a broadband modem through the home-owner's IP backhaul connection. For instance, mobile services are provided through the cellular network, through either a macro cell or a femto cell located within the home or office. Wireless local area network (WLAN) access points (APs) provide data connectivity between computers, laptops, printers, etc. using 802.11-based WiFi technology.
The 802.11 direct link setup (DLS) standards support a direct link feature which allows a bidirectional connection from one STA to one peer STA such that frames do not pass through an AP. Once the direct link has been set up, all frames between the two STAs may be exchanged directly. This direct link provides a means for efficiently using the wireless medium as traffic does not need to be routed through the AP.
IEEE Standard 802.11z defines a TDLS protocol, which can be used to set up a direct link between STAs that are associated with a same AP. The main objective of 802.11z is to provide an AP-independent DLS. DLS signaling frames are encapsulated in data frames so that they are transferred via an AP transparently. This may result in a simplified two-way handshake which does not require any TDLS feature to be implemented within the AP.
There is a potential problem with existing DLS or TDLS protocols. For example, when two SATs communicate with each other using a direct link, one STA in a direct link may suddenly lose its direct link state before it can inform the peer STA. This may be because its software crashes or due to some other unexpected reasons. As a result, the peer STA may not notice that the direct link between the two STAs is lost by itself. It still believes that the direct link is available. Furthermore, the peer STA may still try to send a frame via the non-functional direct link. On the other hand, any frames sent by the peer STA via the non-functional direct link may still get acknowledged on a media access control (MAC) layer if there is no error associated with it. Therefore, there is an ambiguity on the direct link state between these two STAs. For example, the peer STA may send an Acknowledgement (ACK) to the STA. However, after the acknowledged frame and ACK are further analyzed by the STA, both will be discarded because the they are sent on the non-functional direct link with the peer STA. In addition, because there may be another ACK previously sent by the STA and received by the peer STA, the peer STA may not be aware of this breakdown of the direct link between the two STAs. Therefore, there is a need for a mechanism for doing a state synchronization between STAs so that all involved STAs receive an update of which direct link is lost recently.